Microphysical Plasma Processes in Astrophysics

Uppsala 2004

Matter

• More than 99% of all visible matter in the Universe is in the plasma state

• Invisible matter is unknown but weakly (i.e. mainly gravitationally) interacting, thus of importance for structure formation but not of primary importance for life and men

• Locally almost all matter is in a collisionless (if understood as non-anomalous) state

Main Thesis

• If astrophysicist or astronomers could perform only one single measurement in situ this would have desastrous consequences for most astrophysical theories and models

• Astrophysical theories and models would turn out to be basically wrong and would have to be overthrown and replaced by new local theories which should include basic aspects of microphysics

• The relevant microphysics is kinetic plasma physics

Justification

• The paradigm is Space Physics• Almost all physical predictions which in space

physics have been based on purely theoretical reasoning have turned out to be wrong (or at least only marginally correct) after the advent of rocket and spacecraft measurements in situ

• In situ measurements have generated an entirely new and before unknown and unimaginable world of problems in space physics

• This fact demonstrates the lack of imagination in human thinking and reasoning

Problems

• Reconnection

• Jet stability

• Interacting plasma shells

Particle acceleration

Radiation

Reconnection

• Reconnection in almost all astrophysical systems is collisionless

• Resistive reconnection is a myth unless the matter is dominated by neutrals

• If this is correct then MHD does not apply to reconnection independent of scales

Estimates

Presence of Neutrals

mfp =1/ nnc

For resistive reconnection:

mfp < c/pi

pi = ion plasma frequency

n/nn < nc/pi

Weakly ionized plasma only!

Fully Ionized Plasma

mfp = 64D(ND/lnND)

ND » 1

64D(ND/lnND) < c/pi

ND < c/v

Only satisfied for very low temperatures T~0

Reconnection in fully ionized plasma is always collisionless!

W/nT > (m_e/m_i)1/2ve/c

anomalous or Bohm diffusion

Example: Reconnection on the Sun

N~ 1016 m-3

T~50-100 eVve ~ 10000 km/s

e-i ~ 700 Hzc/pe ~ 10 cm

c/pi ~ 5 mmfp ~ 1-10 km

Solar atmosphere is absolutely collisionless what concerns any reconnection taking place there!

Broadband Noise Spectra in Turbulence behind Shocks

Pickett et al. Ann. Geophys. 10, 2003

Solitons in Post-Shock-Turbulence and their Spectrum

Pickett et al. Ann. Geophys. 10, 2003

Parallel Electric Fields/Potential Drops and Particle Acceleration

Ergun et al. PoP. 9, 2002

Solitons in low-ß Regions

Ergun et al. PoP. 9, 2002

McFadden et al. JGR. 108, 2003

Electron Modulation in Solitons

McFadden et al. JGR. 108, 2003

Magnetospheric Field Line Structure (Empirical Tsyganenko Model)

X (RE)

Z (

RE)

Solar Wind

B

X-point

Magnetopause

Magnetosheath

Bow S

hock

Lobes

1

3

2

1

3

The Meaning of Reconnection

Axford 1984

Generalized Ohm´s Law(Fluid Approach)

E + v B - j = (0pe2)-1t j + (jv + vj – (en)-1j j)} + (en)-1{ j B - Pe + Fepmf

Inertial term Hall term Wave pmf

In quasi-equilibrium the electron pressure gradient term is the ion pressure term, for then:

j B - Pe ·Pi

Assumptions: two-fluid (protons/electrons)

ideal conditions ~ collisionless

me/mi <<1, 0

[ Wave ponderomotive force usually neglected without justification (?)

May be important in a turbulent plasmasheet ]

Reconstruction of Hall Current System in the Magnetotail (Nagai et al., 1998, 2001)

Electron Hall Current System i

Unmagnetised Ions

Unmagnetised Electrons

e

Hall-Effect in Magnetotail 2

Oieroset et al., Nature 412, 416, 2001 Received 1. May 2001

Electron Acceleration in Magnetotail Reconnection

Oieroset et al. (2002)

FAC‘s connected to Hall Current

Wrong !No Hall current !

Reconnection Region

Acceleration of Electrons

Lower-hybrid Waves at Magnetopause

Bale et al., GRL 24, 2180, 2002

Guide Field Simulation

Drake et al. Science 299, 2003

Solitons in Reconnection Connected Boundary

Cattell et al. GRL 26, 1999

M87 Radiolobes around a central Black Hole

Cygnus A und B0218+357 Radiolobes

Radiogalaxien

Halpha

Bild

Seyfert2G ESO428-g14 NGC6946 (6 cm)

M84(4.9 GHz)Mk34

Synchrotron Radiation in Reconnection

EII

Fe()

P()

Synch-spectrum

Particle Acceleration by Electric Fields

Particle Acceleration by Electric Fields

Electric Wave Forms and Spectra

Solitons

Radiation Fine Structure

Phase Space Distribution

Distributions and Holes

Hole Dynamics in Radiation Source

The Inefficiency of the Loss-cone Maser

Small Growth of Loss-cone Maser